Serialize subclass with Json.NET

Question

I am trying to use Json.NET to serialize a subclass. The resulting json contains the serialized properties for the superclass but not the properties on the subclass object.

This seems to be related to an issue I found here on SO. But having to write a JsonConverter seems like overkill.

Sample subclass:

public class MySubclass : List<string>
{
    public string Name { get; set; }
}

Sample of the serialization:

MySubclass myType = new MySubclass() { Name = "Awesome Subclass" };
myType.Add("I am an item in the list");

string json = JsonConvert.SerializeObject(myType, Newtonsoft.Json.Formatting.Indented);

Resulting json:

[
  "I am an item in the list"
]

I expected to result to be more like this:

{
    "Name": "Awesome Subclass",
    "Items": [
        "I am an item in the list"
    ]
}

Perhaps I am just not using the right configuration when serializing. Anyone have any suggestions?

I am trying to move away from an XmlSerializer for multiple reasons, but mainly for performance. Currently I am serializing objects using an XmlSerializer and implementing IXmlSerializable because I have complex generic interface properties that are being serialized (which can't be deserialized without implementing IXmlSerializable). Json.NET is fast and it will allow me to serialize/deserialize this same object without having to do custom serialization. The downside is that I just found out it won't serialize properties on a subclass of IEnumerable. — Adam Spicer
– Adam Spicer, Commented Jul 6, 2012 at 18:59

Paolo Moretti · Accepted Answer · 2013-10-10 15:59:16Z

5

According the documentation:

.NET lists (types that inherit from IEnumerable) and .NET arrays are converted to JSON arrays. Because JSON arrays only support a range of values and not properties, any additional properties and fields declared on .NET collections are not serialized.

So, don't subclass List<T>, just add a second property.

public class MyClass 
{
    public List<string> Items { get; set; }
    public string Name { get; set; }

    public MyClass() { Items = new List<string>(); }
}

edited Oct 10, 2013 at 15:59

answered Jul 6, 2012 at 18:50

Paolo Moretti

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1 Comment

Adam Spicer Over a year ago

Thanks for the note from the documentation. It looks like I can't use the classes that I was using for XmlSerialization unless I modify them so that they no longer inherit from an IEnumerable class.

Kevin Aenmey · Accepted Answer · 2012-07-06 18:49:59Z

2

Here are my thoughts on this. I would think that your expected results would be more consistent with a class like this:

public class MyClass 
{
    public string Name { get; set; }
    public List<string> Items { get; set; }
}

I would not expect to see an Items element in the serialized result for MySubclass : List<string> since there is no Items property on List nor on MySubclass.

Since your class MySubclass is actually a list of strings, I would guess (and I am just guessing here) that the SerializeObject method is merely iterating through your object and serializing a list of strings.

answered Jul 6, 2012 at 18:49

Kevin Aenmey

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